Why Drug Interactions Matter with Amphetamine XR

If you take Amphetamine XR for ADHD, it's important to know that this medication can interact with other drugs, supplements, and even certain foods. Some interactions are minor, but others can be life-threatening.

This guide covers the most important interactions to be aware of, including prescription medications, over-the-counter products, supplements, and food — so you can have an informed conversation with your doctor and pharmacist.

How Drug Interactions Work

A drug interaction happens when one substance changes how another substance works in your body. With Amphetamine XR, interactions can:

• Increase amphetamine's effects — making side effects worse or potentially dangerous
• Decrease amphetamine's effects — making the medication less effective for treating ADHD
• Create new risks — such as serotonin syndrome or dangerously high blood pressure

Amphetamine XR is metabolized in part by the CYP2D6 enzyme system and is affected by urinary pH, which means both other medications and your diet can change how much of the drug stays active in your body.

Prescription Medications That Interact with Amphetamine XR

MAOIs (Monoamine Oxidase Inhibitors) — Contraindicated

This is the most dangerous interaction. Do not take Amphetamine XR if you have used an MAOI within the past 14 days. MAOIs include medications like phenelzine (Nardil), tranylcypromine (Parnate), and selegiline (Emsam). Combining these drugs with amphetamine can cause a hypertensive crisis (dangerously high blood pressure) or serotonin syndrome — both of which are medical emergencies.

Serotonergic Medications — Risk of Serotonin Syndrome

Taking Amphetamine XR with drugs that increase serotonin can cause serotonin syndrome, a potentially life-threatening condition. Symptoms include agitation, confusion, rapid heart rate, muscle twitching, sweating, and high fever. Medications in this category include:

• SSRIs — fluoxetine (Prozac), sertraline (Zoloft), escitalopram (Lexapro)
• SNRIs — venlafaxine (Effexor), duloxetine (Cymbalta)
• Tricyclic antidepressants — amitriptyline, nortriptyline
• Triptans — sumatriptan (Imitrex), rizatriptan (Maxalt)
• Other serotonergic drugs — fentanyl, lithium, tramadol, buspirone

Many people with ADHD also take antidepressants, so this interaction is especially important to discuss with your doctor. In some cases, these medications can be used together with careful monitoring — but your doctor needs to know about all of them.

CYP2D6 Inhibitors

Drugs that inhibit the CYP2D6 enzyme can increase amphetamine levels in your blood, raising the risk of side effects. Examples include quinidine, ritonavir (Norvir), and paroxetine (Paxil). If you take any of these, your doctor may need to adjust your Amphetamine XR dose.

Blood Pressure Medications

Amphetamine XR can raise blood pressure and heart rate, which may reduce the effectiveness of antihypertensive medications. If you take blood pressure medication, your doctor should monitor you more closely after starting Amphetamine XR.

Supplements and Over-the-Counter Medications

Some common supplements and OTC products can also interact with Amphetamine XR:

• St. John's Wort — A popular herbal supplement for mood that increases serotonin. Taking it with Amphetamine XR raises the risk of serotonin syndrome. Avoid this combination.
• Vitamin C (ascorbic acid) — High-dose vitamin C acidifies the urine, which increases how quickly amphetamine is eliminated from the body. This can make the medication less effective. Avoid taking large doses of vitamin C at the same time as your medication.
• Antacids — Products containing sodium bicarbonate or other alkalinizing agents can increase amphetamine absorption and blood levels, potentially increasing side effects.
• Proton pump inhibitors (PPIs) — Common acid reflux medications like omeprazole (Prilosec) may alter Amphetamine XR absorption.

Food and Drink Interactions

What you eat and drink can also affect how Amphetamine XR works:

• Citrus juice and acidic foods — Orange juice, grapefruit juice, and other acidic beverages can reduce amphetamine absorption and effectiveness. Try to avoid consuming large amounts of citrus near the time you take your medication.
• Caffeine — Coffee, energy drinks, and caffeinated teas can amplify the stimulant effects of Amphetamine XR, leading to jitteriness, increased heart rate, anxiety, and trouble sleeping. While you don't necessarily have to eliminate caffeine entirely, be mindful of how much you consume.

A practical tip: Take Amphetamine XR with water (not juice) in the morning, and wait at least an hour before having coffee or citrus.

What to Tell Your Doctor

Before starting Amphetamine XR — or at any follow-up appointment — make sure your doctor knows about:

1. Every prescription medication you take, including psychiatric medications, blood pressure drugs, and pain medications
2. All over-the-counter products, including antacids, cold medications, and pain relievers
3. Supplements and herbal products, especially St. John's Wort, vitamin C, and any herbal energy or mood supplements
4. Your caffeine intake — how much coffee, tea, or energy drinks you consume daily
5. Any new symptoms — particularly rapid heart rate, confusion, muscle twitching, or mood changes that could signal an interaction

It's also a good idea to use the same pharmacy for all your medications. Your pharmacist runs automatic interaction checks each time a prescription is filled and can flag potential problems.

Final Thoughts

Drug interactions with Amphetamine XR are manageable, but only if your healthcare team knows what you're taking. The most critical thing to remember: never combine Amphetamine XR with MAOIs, and always tell your doctor about serotonergic medications.

For more information, learn about what Amphetamine XR is and how it's used, review its side effects, or find a doctor who can prescribe it. If you need to fill your prescription, Medfinder can help you locate a pharmacy with stock.